[MITgcm-support] layers and ptracers

Ryan Abernathey ryan.abernathey at gmail.com
Wed Jul 20 06:59:08 EDT 2016

Hi Dan,

I would like to diagnose along-isopycnal and cross-isopycnal fluxes of a
> passive tracer.

This is a great idea and an important application.

> One possible solution is to use the 'layers' package together with the
> 'ptracers' package.  My impression from the source code is that this is not
> currently supported (i.e. the only mention of 'ptracers' in the 'layers'
> source code is in a section that is commented out).

The layers documentation still needs to be written. That was on my list for
summer (which is now more than half over!).

> My questions are:
> - Is it true that "layers" does not currently support passive tracers?

It's not clear exactly what you mean by "support". But regardless, layers
doesn't do anything with ptracers. If you would like the do the full tracer
budget in isopycnal coordinates, it will be a major undertaking.

- If layers does not currently support ptracers, does anyone happen to be
> working on that?

I'm definitely not working on it.

> I guess it should be straightforward to generalize, since 'theta' and
> 'salt' are tracers as well.

Be careful here. Theta and Salt are tracers, but layers doesn't allow you
to do heat or salt budgets in isopycnal coordinates either. It allows you
to use Theta or Salt as the layers coordinate itself. It would be
relatively easy to extend layers to allow ptracer to be the vertical
coordinate. In contrast, it will be quite involved to do the full ptracer
budget in isopycnal (or Theta or Salt) coordinates. I hope the difference
is clear.

One approach would be to first create a package called BUDGETS, which
implements diagnostics for the TENDENCIES of the tracers due to various
processes (advection, diffusion, forcing, etc.). (This would be very useful
in its own right.) Then you could create a layers routine to interpolate
any diagnostic into "layers space". That would be a very general approach
which could also eventually lead to the isopycnal momentum budget.

However, if you want to decompose the advection of a ptracer into along and
across-isopycnal, it will be truly hard to obtain a closed budget.

I would be happy to chat with you about these strategies via Skype if you


> Best,
> Dan
> --------------------------------------------------------------
> Dr Dan Jones
> Polar Oceans Team
> British Antarctic Survey
> Phone: +44 (0)1223 221505
> Skype: dcjones.work
> http://www.bas.ac.uk/profile/dannes/
> Cambridge Centre for Climate Science
> <http://www.climatescience.cam.ac.uk/>
> http://www.climatescience.cam.ac.uk/
> --------------------------------------------------------------
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> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
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